1. Field of the Invention
The present invention relates to a combination container and pump, i.e., a pump assembly having a container for storing a liquid such as a chemical solution and air in an isolated relationship, and a pump for discharging the liquid from the container when required.
2. Description of Background Art
FIG. 8 of the accompanying drawings shows a conventional combination container and pump.
As shown in FIG. 8, the conventional combination container and pump, generally denoted at B, comprises a container a, a pump b, and a piston c slidably disposed in the container a. The interior of the container a is sealed by the pump b at the top thereof and the piston c at the bottom d thereof.
The pump b is of the type generally referred to as an airless pump, as disclosed in Japanese Laid-Open Patent Publication No. 61(1986)-263668. When a depressing member e of the pump b is depressed, the pump b operates to draw a stored liquid X from the container a and discharge the liquid X out of the container a.
More specifically, the liquid X filled in the container a is discharged out of the container a by the pump b when the depressing member e in the upper portion of the pump b is depressed with a finger. When the X egresses out of the container a, the amount of the liquid X stored in the container a is reduced, allowing the piston c to move upwardly in the direction indicated by the arrow in FIG. 8 while a pressing lip f of the piston c is being pressed against the inner wall surface of the container a in a sealing relationship. Since the liquid X filled in the container a is not exposed to ambient air, it can be stored in an isolated condition.
The combination container and pump B may be filled with the liquid X as follows: The pump b is first mounted in the container a. Thereafter, in a vacuum, the liquid X is introduced into the container a through the open bottom d while the bottom d is being directed upwardly. Then, the piston c is inserted into the bottom d, sealing the container a. This filling process, however, requires a large complex filling apparatus.
Alternatively, the piston c may first be inserted into the bottom d and then the liquid X may be introduced into the container a through the top thereof, after which the pump b may be mounted in the top of the container a. One problem of this filling procedure is that air may be trapped in the container a when the pump b is inserted after the liquid X has been filled.
Air bubbles which have been included in the liquid X filled in the container a are responsible for oxidation of the liquid X in the container a and contamination of the filled liquid X with microorganisms contained in the air. To avoid such drawbacks, therefore, it has been necessary to replace any air trapped when the liquid X is filled in the container a, with nitrogen.
The pressing lip f extends fully around the upper circumference of the piston c. The pressing lip f is pressed against the inner wall surface of the container a, thereby sealingly retaining the liquid X in the container a. The piston c is made of a relatively hard synthetic resin such as polyethylene or the like. Since the piston c is slidable in the container a while sealing the interior of the container a, the pressing lip f is required to be relatively thin so that it is given a suitable degree of resiliency.
However, the thin pressing lip f made of a synthetic resin, e.g., polyethylene, cannot easily be shaped to a configuration which keeps the interior of the container a suitably sealed. The thin pressing lip f is usually not shaped with high accuracy. Moreover, the thin pressing lip f tends to be deformed as the temperature changes. The pressing lip f thus deformed allows the liquid X to leak from the container a past the piston c.